Oil well swabbing procedures known in the art primarily involve the initiation of the flow of oil from a new well. After a well has been drilled through oil bearing sands, a pipe or casing is placed in the drilled hole and the lower portion of the pipe is cemented in place by pumping a certain amount of cement down the pipe, out of the bottom, and up along the outside of the pipe through the region of the oil bearing sands. After the cement is in place, a rubber plug is pumped down the pipe to clear the cement from the inside of the pipe, and the plug remains at the bottom immersed in cement. When the cement has set, holes are shot at right angles to the pipe into the oil bearing sand zone. Generally, because the oil sand zone is of a porous nature, the sands have absorbed some of the cement and partially sealed the area. Hydrochloric acid followed by salt water is then pumped down the pipe to open the area, and the swabbing tool and procedure is then used to remove the acid, salt water and any sand in the pipe, and to create a partial vacuum in the oil sands area in an attempt to start the flow of oil from the oil sands formation.
The swabbing tool comprises a mandrel which is a pipe generally about six feet long with a stop or cup retainer on each end thereof. Generally, four swabbing cups are slidably mounted on the mandrel, and the mandrel is lowered and raised in the oil well pipe by a cable controlled by a winch. An operator of the winch lowers the mandrel and the swabbing cups carried thereon to the bottom of the oil well pipe below the acid, salt water and sand in the pipe and then raises the mandrel and cups to carry the liquids and sand thereabove to the surface of the ground for disposal. As the mandrel is raised, a partial vacuum is created in the oil well pipe below the mandrel which tends to draw oil from the oil sands formation. That procedure is repeated many times until the well starts to flow or is swabbed dry of all liquids.
The prior art swabbing cups consist of an annular rubber member having an outer diameter initially substantially equal to the inner diameter of the oil well pipe and are shaped so that the rubber will flex toward the mandrel as it is lowered through the liquids in the oil well pipe and will flex outwardly against the oil well pipe under the weight of the column of liquids thereabove as it is raised in the oil well pipe. The necessary repeated lowering and raising of the mandrel and cups causes relatively rapid wear of the periphery of the cup with the consequent loss of its ability to raise a column of liquid and to create the necessary partial vacuum. Disassembly of the mandrel to remove and replace worn cups is a relatively expensive procedure including the time lost during the down time of the equipment while the cups are being replaced.
The subject invention comprises a swabbing cup construction which is easily manually adjustable for wear in use, and a method which greatly increases the efficiency and reduces the cost of oil well pipe swabbing operations.